Weed farms don’t waste as much water as researchers previously thought

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Legal cannabis growers don’t use as much water as researchers previously thought, according to a recent study published in the Journal of Environmental Management.

To better understand the environmental impact of large-scale cannabis production, the University of California’s Cannabis Research Center at Berkeley began tracking the exact amount of water used by the state’s legal cannabis farms. Starting in 2017, researchers began collecting data from state-licensed cannabis growers and supplementing this information with anonymous interviews with weed growers.

“There is growing concern about the effects of cannabis farming on the environment, and particularly on water resources, but data on cultivation practices and water use patterns have been limited,” the study authors explain. “Estimates of water use for growing cannabis have previously been based on extrapolated values ​​of plant water requirements that do not take into account differences in growing practices, fluctuations during the growing season, or the role of water storage in changing seasonal extraction patterns.”

These early estimates suggested that cannabis farms could be consuming a large portion of the Golden State’s limited water resources, but the study found that these concerns were exaggerated. On average, a legal pot cultivator uses the same amount of water as a tomato grower. And while the average vegetable farm spans thousands of acres, most weed farms take up less than half an acre of land.

“Our research has shown that cannabis is not particularly thirsty compared to other plants,” Ted Grantham, co-director of the Cannabis Research Center and co-author of the study, told the PPIC Water Policy Center. “And cannabis farms are considerably smaller than other plants – about a quarter of an acre on average. So cannabis has a very small footprint and makes up only a fraction of the total water used by California’s agriculture. “

Natalynne DeLapp, executive director of the Humboldt County Growers Alliance, told the Times-Standard that this research “is really timely considering the importance of these talks right now,” especially now that the state is in the midst of a severe drought. “I think some people have the idea that cannabis is a particularly thirsty plant and that was never true. Now that we’ve been legalized for a few years and have more data, it’s good to see this reflected in academic research. “

“Many farmers fear drought and are concerned about the long-term effects of climate change on our community and the environment,” she added. “It is also known that we are likely to see more of this in the future, so there is great interest in long-term climate resilience planning that includes increased water storage capacity and improved water efficiency measures.”

Unfortunately, this research only focuses on legal growers who represent only a small fraction of the grass currently grown in California. Recent estimates suggest that illegal weed farms produce more than 10 million tons of black market weed each year, and that cultivation does not have to comply with existing state water regulations. To make matters worse, most of these farms also use toxic pesticides, which can poison the surrounding land, kill local wildlife, and seep into waterways.

“We’re approaching 8,000 legal cannabis farms in the state, including permitted indoor and outdoor grows. But most farms across the country are not allowed, ”Van Butsic, co-director of the Cannabis Research Center, told the PPIC. “To give you an impression of the size, we estimate that the counties of Humboldt and Mendocino alone had around 15,000 illegal farms in 2018.”

“Cannabis regulations aim to reduce the impact on water use – including restrictions on when farmers can divert from streams and on-site storage requirements when they rely on surface water sources. However, unauthorized establishments do not necessarily follow these practices, ”said Grantham. “If a grower is legal, the water source is legal (and managed). In the case of illegal cultivation, it is not clear where the water comes from. “

For future research, the study’s authors hope to collect data from these illegal farms in order to improve “an overall understanding of cannabis water use practices and the impact on the environment”.